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Tuesday, February 28, 2012

Palisades - some general comments.

Over the last several months, I have received numerous questions about Palisades Nuclear Power Station which is located near South Haven, Michigan and which is presently operated by Entergy Nuclear Operations. I have until now declined to comment as most of the inquiry has concerned personnel issues, which are all too well described in the various NRC releases and findings which the press have seized upon. Since these things are well covered there has been no need to respond. However, a new allegation has arisen which is similar to one I confronted about a plant in Japan some time back. First, some background.

Palisades is a Combustion Engineering pressurized water plant which was ordered by Consumers Power in January 1966. According to an official Palisades press kit issued by Combustion Engineering and Consumers Power which I have here, Palisades was the first nuclear station in the United States that was not a "turn key" project contracted to a single firm; rather, Consumers Power contracted Bechtel Corporation for general consulting and engineering services, and the two firms, working closely, independently ordered all of the equipment required to construct the station. Original plans called for four identical units at the site, but only one was ever begun. This plan did lead to the single completed plant being referred to as "Palisades Unit 1" in some publications in the late 60's and early 70's which could lead to some confusion if this fact wasn't clearly described.

The reactor thermal output as built was 2200 MWt; the Westinghouse turbine generator at that reactor power produced 710 MWe of power although it was rated at 845 MWe maximum. The 2008 data for the plant are a reactor thermal power of 2565 MWt and a corresponding net electrical output of 778 MWe. Modern data from Entergy indicates a net electrical output of 798 MWe. When this plant was built, Consumers Power had been operating Big Rock Point Nuclear Plant since 1962 (this was a GE BWR/1 plant.) Consumers Power was also at that time building the Midland nuclear station, a two-unit Babcock & Wilcox plant that was never finished.

Palisades achieved initial criticality May 24, 1971 - about a year behind the original ambitious schedule. The plant first delivered power commercially on December 31, 1971 (both dates according to WASH-1203-73, US AEC 1973.) Like many other plants, Palisades had some initial problems that had to be ironed out but they weren't nearly as bad as those at some other plants built both before and after.

Palisades' earliest serious unplanned outage took place starting at about the middle of 1973 to repair leaks in "B" steam generator. The photo here, courtesy AP and which is an old AP Wirephoto, shows Palisades in October 1974 while undergoing testing after the year long outage. Notable is the addition of cooling towers - these were not a part of the original plant design which used only lake water for plant cooling. The Combustion Engineering - Consumers Power press kit (which is from early 1970) makes no mention of, and does not show, any cooling towers. Note the excavated area beyond the plant where the second unit would have been constructed.

Entergy bought this plant from Consumers Power in April, 2007.

So now we have a bit of background on Palisades - which I might add showed a very high capacity factor of 99% as recently as 2008. More recent problems have put the plant in a bad light, and local activist press has not helped. We now bring to focus the following commentary found on line:

This commentary needs some sober observation and reflection. This exact same kind of argument was brought up some time back concerning Genkai nuclear station in Japan. I conducted a VERY thorough description of reactor vessel embrittlement on Atomic Power Review at that time - and it's applicable here.

While much of the above discussion is targeted at Genkai, it's all generally applicable to Palisades and relative to the commentary I linked. Some points in the linked commentary:

-The NRC has never weakened safety regulations. When new analyses are made, then old ones which are less accurate are reconsidered. This process can both help and hinder relicensing processes for plants.

-No "old, degraded" reactors are operating. None exist.

-The phenomenon of PTS or "Pressurized Thermal Shock" was originally developed in the early 1980's after two incidents (one at Palo Verde, the other at Crystal River) gave evidence that there was a remote chance that the design basis accident causal mode known as brittle fracture (this being relative to the reactor pressure vessel) which had never happened even once could possibly be induced by a pressurized thermal shock sequence wherein a pressure vessel was taken from hot, critical normal condition through a rapid cooldown and depressurization, and then a rapid repressurization. The fear was that while no vessel had ever experienced the dreaded brittle fracture failure, so that this eventuality (still designed against) became highly unlikely, there could be some other chain of events that would essentially duplicate it but would be much less immediate, more nuanced, and harder to prevent. As it turns out, there were massive discussions about PTS in some quarters during the first half of the 1980's but as a practical matter later, much better knowledge of how pressure vessels age has lowered concerns... largely through the use of sample materials placed in high neutron flux areas inside reactors, which samples are then removed and tested exhaustively.

According to Gregory Myerson the NRC found a solution to any serious worry about PTS was to order alteration to the alloy used to fabricate reactor vessels and did so as early as 1971 - while monitoring any vessels built prior exceedingly carefully to ensure they don't pose any increased risk. To date, none has been identified.

The commentary then soars off into ridiculousness, with every incredible worst-case type assumption and scenario being topped by the next one. As such it's easily recognizable as anti-nuclear hyperbole and hype. But... what DID the NRC resident inspector really say?

Probably, the inspector wished to convey that neutron damage to a pressure vessel really consists of the displacement of atoms from their normal positions in the crystalline metal structure or lattice. This makes essentially gaps that are one atom wide. Not exactly the holes this commentary describes. Moreover, this damage is easily designed against by careful control of materials used in the pressure vessel, careful manufacturing and extremely generous allowance for the effect of the damage over decades so that even with embrittlement the vessel still behaves normally and can handle the original specified temperatures and pressures. Some plants have very old vessels which require some modification of the allowed rate that you can heat up or cool down the vessel - but this is normal for very old vessels, frankly. As mentioned in my Genkai article, so much monitoring and study is being done and has been done that vessel embrittlement is probably one of the most studied metallurgical phenomenon to come out of the whole history of nuclear engineering.

Left, reactor vessel and internals, Palisades Nuclear Power Station, as originally built.

Getting now to the present NRC findings - which have far more substance than the allegations of embrittlement - there will be a public meeting tomorrow night (February 29, 2012) that will likely gain some attention. Click here to read one article about the meeting. Click here to read another. I will be watching to see what comes out of these meetings and report on it here. It suffices to say that the personnel issues brought up seem to have more substance than any of the reactor vessel issues the activists are attempting to invent. It is those on which the attention must be cast.

NOTE: Some questions were received about San Onofre, in California, which also has Combustion Engineering plants whose (new) steam generators were found to be leaking very recently. These new steam generators were built by Mitsubishi in Japan, and so there is no direct correlation at all between the primary-secondary leaks at San Onofre and any other Combustion Engineering plant.